A Novel Coding Phase Gradient Metasurface for Wideband RCS Reduction

In this letter, a new design of metasurface based on coding phase gradient meta-surface for wideband radar cross section (RCS) reduction is proposed. The unit cell of the metasurface is composed of a Jerusalem structure and a central circular ring. In order to reduce the burden of the computation time and to optimize design procedure, we use the genetic algorithm and nonlinear fitting method to determine the unit cell geometer. By changing and selecting the parameter of each unit, it is found that the reflection phase of the unit can achieve a stable distribution of phase gradient of the cell among the frequency range of 7.5-26 GHz. In our design, both the random coding sequences and gradient phases in the coding elements are combined to manipulate the EM waves. Four kinds of super-cells with different gradient directions are obtained according to the generalized Snell's Law, serving as the coding element. A coding metasurface composed of 6 × 6 supercells with random arrangement is designed to improve its RCS reduction. By coding four types of linear-phase gradients in a random pattern, reflected wave can be uniformly diffused. Moreover, the manipulation of waves will be more flexible compared with other designs. The simulated results show that a 10 dB RCS reduction is realized over broadband ranging from 7.5 to 26 GHz.